1. Field of the Invention
This invention relates to a process of producing ammonium polysulfide (APS) in at least one electrochemical cell, to which an aqueous ammonium sulfide solution is supplied as electrolyte, and from which an APS-containing solution is withdrawn.
2. Description of Related Art
Such process is known from EP-A-0 226 415 and from DE-C-43 06 445. The object underlying the invention is to create an inexpensive and at the same time efficient process which provides for an increased production of APS. In accordance with the invention, this is achieved in the above-stated process in that the cell comprises an anode, a gas diffusion cathode, and between the anode and the cathode an electrolyte chamber, the cell voltage being 0.01 to 5V, that the cathode has an electrically conductive, gas-permeable carbon layer, over which flows gas containing free oxygen, and which is in contact with the electrolyte, that gas containing free oxygen is introduced into the electrolyte chamber, where hydroperoxide anions (OOH.sup.-) are formed in the electrolyte chamber, and that an APS-containing solution and a residual gas are withdrawn from the electrolyte chamber. The ammonium polysulfide has the chemical formula (NH.sub.4).sub.2 S.sub.x, where x is in the range from 2 to 6. The pressure in the cell can be in the range from 0.1 to 20 bar, and in a special embodiment up to 60 bar. Such process is known from EP-A-O 226 415 and from DE-C 43 06 445.
In the process in accordance with the invention, the APS is produced in the electrochemical cell simultaneously in three different ways A, B, and C as follows: